Siemens 7SJ85 - Page 738

Parameter Value Description
fundamental comp.
Select this method of measurement to suppress harmonics or transient
voltage peaks.
Siemens recommends using this parameter value as the default setting.
RMS value
Select this method of measurement if you want the stage to take harmonics
into account (for example at capacitor banks). Do not set the threshold
value of the stage under 10 V for this method of measurement.
Parameter: Measured value
•
Recommended setting value (_:421:9) Measured value = phase-to-phase
With the Measured value parameter, you define whether the stage monitors the phase-to-phase voltages
V
AB
, V
BC
, and V
CA
, or the phase-to-ground voltages V
A
, V
B
, and V
C
. Parameter Value
Parameter Value Description
phase-to-phase
If you want to detect voltage dips caused by multiphase short circuits, or
generally monitor the voltage range, keep phase-to-phase as the default
setting. The function will not pick up on ground faults.
Siemens recommends the measured value phase-to-phase as the
default setting.
phase-to-ground
Select the phase-to-ground setting if you want to detect voltage unbal-
ances or overvoltage conditions caused by ground faults.
Parameter: Threshold
•
Default setting (_:421:3) Threshold = 80 V
The Threshold is set in accordance with the Measured value as either a phase-to-phase or phase-
to-ground variable.
Specify the Threshold (pickup threshold) for the specific application.
For the default setting, the lower limit of the voltage range to be monitored is assumed to be 80 % of the
rated voltage of the protected object.
EXAMPLE:
Rated voltage of the protected object: V
rated, obj.
= 10 kV
Voltage transformer:
Threshold value: 80 % of V
rated, obj.
The secondary setting value is calculated as follows:
[foschwlw-190309-01.tif, 2, en_US]
Parameter: Pickup mode
•
Recommended setting value (_:421:101) Pickup mode = 1 out of 3
With the Pickup mode parameter, you specify whether the stage picks up when there is a lower threshold-
value violation in one measuring element (1 out of 3) or when there is a lower threshold-value violation in
all 3 measuring elements (3 out of 3).
Protection and Automation Functions
6.29 Undervoltage Protection with 3-Phase Voltage
738 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017